A balanced lever has two weights on it, the first with mass #3 kg # and the second with mass #4 kg#. If the first weight is # 8 m# from the fulcrum, how far is the second weight from the fulcrum?
6 m away from the fulcrum, opposite from the first weight.
For the lever to be "balanced", there must be no net torque on the system, or
Assuming the fulcrum is at the center of mass of the lever (or the lever is massless), the torques created by each of the weights must be equal and opposite:
Torque is the force perpendicular to a point of rotation multiplied by the distance from that pivot point. Assuming the lever to be horizontal, the torque equation becomes:
Applying the given information, we get:
The fact that
The second weight must be positioned 6 m away from the fulcrum on the other side of the fulcrum.